Vascular disease, including peripheral athersclerosis and coronary artery disease, is one of the major health problems in this country. Each year, over 600,000 vascular procedures are performed in the United States. The main clinical problems associated with these procedures are occlusion and restenosis, which must usually be corrected by repeat surgery. The long- term objective of this study is to provide pharmacologic approaches that will reduce the incidence of failure of prosthetic arterial grafts. The technique of seeding the inner surface of the graft with autologous vascular endothelial cells (EC) has improved peripheral graft patency, but graft failure still occurs. The hypothesis of this study is that thrombotic occlusion (clotting) and restenosis (closure) due to neointimal fibrous hyperplasia (NFH) are both due to attack of neutrophils on seeded EC, preventing them from forming a confluent, quiescent graft lining. Proliferating EC produce neutrophil chemoattractants, which are thrombogenic, and smooth muscle cell growth factors, which lad to NFH. The specific aims of the project are to: 1) develop an in vitro system, in which cultured human umbilical vein EC are exposed to activated neutrophils, to test the efficacy of various drugs and monoclonal antibodies at inhibiting neutrophil-mediated damage to and detachment of EC; 2) further test the ability of pharmacologic agents and graft coatings to inhibit EC detachment by neutrophils when the EC are subjected to controlled shear forces in an in vitro flow system; and 3) to test the effectiveness of drugs and graft coatings in improving EC retention and growth on seeded grafts and suppressing smooth muscle cell proliferation in an in vivo canine surgical model in which the grafts are implanted in the carotid artery. Drugs to be tested will include lipoxygenase inhibitors, adenosine receptor agonists, and monoclonal antibodies to neutrophil surface molecules involved in EC attachment. They will be screened in an in vitro system in which assays will be performed for neutrophil superoxide production and granule release, as well as for neutrophil attachment to EC, sublethal damage to EC, and EC detachment. Cell attachment proteins, such as laminin, type IV collagen, and Matrigel, will be tested for the ability to enhance EC retention in vitro on seeded grafts under controlled shear, with pre-exposure of seeded grafts to activated neutrophils. Promising drugs and graft coatings will be tested in vivo for improvement of EC retention during a 6 hour perfusion and enhancement of EC growth and suppression of smooth muscle cell growth during perfusion for up to 30 days.